Single-frequency laser system and optical clock and optical tweezers comprising same

Abstract

The invention provides a single-frequency laser system and an optical clock and optical tweezers comprising the single-frequency laser system, a first single-frequency laser of the single-frequency laser system is a single-frequency thulium-doped distributed feedback fiber laser, and the first single-frequency laser is used for outputting first single-frequency laser; the thulium-doped optical fiber amplification module is used for receiving the first single-frequency laser and amplifying the power of the first single-frequency laser to form first amplified laser; the second single-frequency laser is used for outputting second single-frequency laser; the erbium-doped fiber amplification module is used for receiving the second single-frequency laser and amplifying the power of the second single-frequency laser to form second amplified laser; the laser beam combining module is used for combining the first amplified laser and the second amplified laser to form combined laser; and the sum frequency module is used for performing sum frequency conversion on the combined laser to form output laser which is output outwards. When the single-frequency laser system is applied to the optical clock, the frequency stability and various performance indexes of the optical clock can be improved; when the method is applied to optical tweezers, the control performance of the optical tweezers on atoms can be improved.

Description

TECHNICAL FIELD

[0001] The application relates to a single-frequency laser system and an optical clock and optical tweezers comprising the same. BACKGROUND

[0002] The strontium atomic optical clock is the highest-precision time frequency standard at present, and the magic light wavelength laser is a core component for realizing the strontium atomic optical clock. The single-frequency laser with a wavelength of 813.428 nm can form an optical lattice potential well with a certain well depth through focusing and colliding, and can perform lattice trapping on the clock transition of cold strontium atoms with super-narrow line width and immune to the Stark frequency shift when tuned to the magic light wavelength, so that the single-frequency laser can be applied to the strontium atomic optical clock and can realize the precise timing effect of 50 billion years of operation with only 1 second error.

[0003] In recent years, more and more reports introduce the superiority of quantum computing, and the central atom quantum computing needs high-power, narrow-line-width, ultra-low-intensity noise optical tweezers to realize the manipulation of atoms, and the single-frequency lasers with wavelengths of 840 nm and 852 nm are necessary lasers for rubidium atom quantum computing. Therefore, the single-frequency laser with a wavelength of 800 nm to 900 nm has important application value in the field of quantum information technology.

[0004] At present, the main ways to obtain 800-900 nm laser are titanium sapphire laser and semiconductor laser. The titanium sapphire laser is a solid laser, which can directly generate high-power single-frequency laser with a wavelength of 800 nm to 900 nm, but has problems such as large volume, complex structure, easy to be disturbed by environment, and needs regular maintenance, and the maximum power can only reach 8 W. The semiconductor laser can also realize 800 nm to 900 nm single-frequency laser output, and has a compact structure and is not easy to be affected by the environment, but the output power is low, and even if combined with a semiconductor optical amplifier, the output power can only reach the order of 5 W. SUMMARY

[0005] The application aims to overcome the defects of low output power, large volume and complex structure of the 800 nm to 900 nm single-frequency laser output in the prior art, and provides a single-frequency laser system and an optical clock and optical tweezers comprising the same.

[0006] The application solves the above technical problems through the following technical solutions:

[0007] The application provides a single-frequency laser system, which comprises a first single-frequency laser, a thulium-doped fiber amplification module, a second single-frequency laser, an erbium-doped fiber amplification module, a laser beam combination module and a sum-frequency module, the first single-frequency laser is a single-frequency thulium-doped distributed feedback fiber laser, and the first single-frequency laser is used for outputting first single-frequency laser; the thulium-doped fiber amplification module is used for receiving the first single-frequency laser and amplifying the power of the first single-frequency laser to form first amplified laser; the second single-frequency laser is used for outputting second single-frequency laser; the erbium-doped fiber amplification module is used for receiving the second single-frequency laser and amplifying the power of the second single-frequency laser to form second amplified laser; the laser beam combination module is used for combining the first amplified laser and the second amplified laser to form combined laser; and the sum-frequency module is used for performing sum-frequency conversion on the combined laser to form output laser which is outputted outward.

[0008] Preferably, the second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser, a single-frequency external cavity semiconductor laser or a single-frequency distributed feedback semiconductor laser.

[0009] Preferably, the first single-frequency laser comprises a thulium-doped fiber provided with a first phase-shifted Bragg grating, the length of the grating region of the first phase-shifted Bragg grating is 20mm-60mm, the phase shift value is 0-2π, and the phase shift position of the first phase-shifted Bragg grating is located in the range of 0-30% of the length of the grating region of the first phase-shifted Bragg grating offset from the center of the first phase-shifted Bragg grating to both sides.

[0010] Preferably, the second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser, and the second single-frequency laser comprises an erbium-doped fiber provided with a second phase-shifted Bragg grating, the length of the grating region of the second phase-shifted Bragg grating is 25mm-60mm, the phase shift value is 0-2π, and the phase shift position of the second phase-shifted Bragg grating is located in the range of 0-30% of the length of the grating region of the second phase-shifted Bragg grating offset from the center of the second phase-shifted Bragg grating to both sides.

[0011] Preferably, the wavelength range of the first single-frequency laser is 1650nm-2150nm, the line width is less than 50kHz, the power is greater than 100uW, and the output laser is polarized light; the second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser, the wavelength range of the second single-frequency laser is 1530nm-1640nm, the line width is less than 50kHz, the power is greater than 100uW, and the output laser is polarized light.

[0012] Preferably, the wavelength of the first single-frequency laser ranges from 1650nm to 2150nm, the line width is less than 50kHz, the power is greater than 100μW, and the output laser is polarized light; the second single-frequency laser is a single-frequency external cavity semiconductor laser, the wavelength of the second single-frequency laser ranges from 1530nm to 1640nm, the line width is less than 50kHz, the power is greater than 100μW, and the output laser is polarized light.

[0013] Preferably, the wavelength of the first single-frequency laser ranges from 1650nm to 2150nm, the line width is less than 50kHz, the power is greater than 100μW, and the output laser is polarized light; the second single-frequency laser is a single-frequency distributed feedback semiconductor laser, the wavelength of the second single-frequency laser ranges from 1530nm to 1640nm, the line width is less than 1000kHz, the power is greater than 100μW, and the output laser is polarized light.

[0014] Preferably, the thulium-doped fiber amplification module comprises at least one thulium-doped amplifier, the thulium-doped amplifier comprises a first pump light source, a first fiber combiner, a thulium-doped gain fiber and a first isolator, the first pump light source emits first pump light, the first fiber combiner is used for coupling the first pump light and the first single-frequency laser into the thulium-doped gain fiber, and the first single-frequency laser is amplified in the thulium-doped gain fiber to form the first amplified laser through the first isolator.

[0015] Preferably, the wavelength of the first pump light is any wavelength in the range from 750nm to 830nm, from 1000nm to 1400nm or from 1500nm to 1800nm, and the core of the thulium-doped gain fiber of the last thulium-doped amplifier is greater than or equal to 10μm.

[0016] Preferably, the erbium-doped fiber amplification module comprises at least one erbium-doped amplifier, the erbium-doped amplifier comprises a second pump light source, a second fiber combiner, an erbium-doped gain fiber and a second isolator, the second pump light source emits second pump light, the second fiber combiner is used for coupling the second pump light and the second single-frequency laser into the erbium-doped gain fiber, and the second single-frequency laser is amplified in the erbium-doped gain fiber to form the second amplified laser through the second isolator.

[0017] Preferably, the wavelength of the second pump light is any wavelength in the range from 900nm to 1030nm or from 1450nm to 1530nm, and the core of the erbium-doped gain fiber of the last erbium-doped amplifier is greater than or equal to 10μm.

[0018] The application also provides an optical clock comprising the single-frequency laser system.

[0019] The application also provides an optical tweezers comprising the single-frequency laser system.

[0020] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0021] The positive and progressive effects of this invention are as follows:

[0022] The aforementioned single-frequency laser system combines a single-frequency thulium-doped distributed feedback fiber laser with a single-frequency erbium-doped distributed feedback fiber laser, a single-frequency external cavity semiconductor laser, or a single-frequency distributed feedback semiconductor laser. It is further integrated with thulium-doped fiber amplification modules and erbium-doped fiber amplification modules, and through sum-frequency effects, achieves single-frequency laser output in the 793.8nm–930.4nm range, with a maximum power of 400W. Simultaneously, it features a compact structure, is less susceptible to environmental interference, and requires no maintenance, making it the optimal solution for achieving high-performance single-frequency lasers in the 800nm–900nm range. Applying this single-frequency laser system to optical clocks can improve their frequency stability and various performance indicators; applying it to optical tweezers can enhance their ability to manipulate atoms. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the single-frequency laser system of the present invention.

[0024] Figure 2 for Figure 1 The diagram shows the structure of the first single-frequency laser in the single-frequency laser system.

[0025] Figure 3 for Figure 1 The diagram shows the structure of the thulium-doped fiber amplification module in the single-frequency laser system.

[0026] Figure 4 for Figure 1 The diagram shows the structure of the second single-frequency laser in the single-frequency laser system.

[0027] Figure 5 for Figure 1 The diagram shows the structure of the erbium-doped fiber amplification module in the single-frequency laser system.

[0028] Figure 6 This is a schematic diagram of the structure of the second single-frequency laser in Embodiment 2 of the single-frequency laser system of the present invention.

[0029] Figure 7 This is a schematic diagram of the structure of the second single-frequency laser in Embodiment 3 of the single-frequency laser system of the present invention.

[0030] Explanation of reference numerals in the attached figures

[0031] First single-frequency laser 1

[0032] Thulium-doped fiber 11

[0033] first phase-shifted Bragg grating 12

[0034] thulium-doped fiber amplification module 2

[0035] thulium-doped amplifier 21

[0036] first pump light source 211

[0037] first fiber combiner 212

[0038] thulium-doped gain fiber 213

[0039] first isolator 214

[0040] second single-frequency laser 3

[0041] erbium-doped fiber 311

[0042] second phase-shifted Bragg grating 312

[0043] first gain chip 321

[0044] high-reflectivity mirror 322

[0045] filter component 323

[0046] output component 324

[0047] second gain chip 331

[0048] grating 332

[0049] erbium-doped fiber amplification module 4

[0050] erbium-doped amplifier 41

[0051] second pump light source 411

[0052] second fiber combiner 412

[0053] erbium-doped gain fiber 413

[0054] second isolator 414

[0055] laser-combining module 5

[0056] sum-frequency module 6 DETAILED DESCRIPTION

[0057] The present application will be further described by way of example with reference to the accompanying drawings.

[0058] Example 1

[0059] As Figure 1The diagram shows the structure of the single-frequency laser system of the present invention. This single-frequency laser system includes a first single-frequency laser 1, a thulium-doped fiber amplification module 2, a second single-frequency laser 3, an erbium-doped fiber amplification module 4, a laser beam combining module 5, and a sum-frequency conversion module 6. The first single-frequency laser 1 is a single-frequency thulium-doped distributed feedback fiber laser, used to output a first single-frequency laser. The thulium-doped fiber amplification module 2 receives the first single-frequency laser and amplifies its power to form a first amplified laser. The second single-frequency laser 3 outputs a second single-frequency laser. The erbium-doped fiber amplification module 4 receives the second single-frequency laser and amplifies its power to form a second amplified laser. The laser beam combining module 5 combines the first and second amplified lasers to form a combined laser beam. The sum-frequency conversion module 6 performs a sum-frequency transformation on the combined laser beam to form an output laser beam.

[0060] A single-frequency distributed feedback fiber laser is an all-fiber structure that generates single-frequency laser light by directly etching a phase-shifted fiber Bragg grating onto the gain fiber. The fiber Bragg grating operates by introducing periodic refractive index modulation into the fiber core. The wavelength reflected by the grating is determined by the period of the refractive index modulation in the core and the refractive index of the fiber, satisfying λ = 2n. eff Λ (where λ is the laser wavelength, n) eff When light passes through a grating (where Λ is the effective refractive index of the fiber core and Λ is the period of refractive index modulation in the core), it undergoes distributed reflection. The phase difference between the reflected light in adjacent refractive index modulation periods is 2π, achieving coherent and constructive phase. When the number of refractive index modulation periods is sufficient, effective reflection of light can be achieved. The introduction of a phase shift in the grating can introduce narrowband transmission peaks into the grating reflection spectrum, thereby enabling single-frequency laser output.

[0061] Among them, the first single-frequency laser 1 is a single-frequency thulium-doped distributed feedback fiber laser, that is, a single-frequency distributed feedback fiber laser whose gain fiber is thulium-doped fiber. For example... Figure 2 As shown, the first single-frequency laser 1 generates a first single-frequency laser by directly etching a first phase-shifted Bragg grating 12 onto a thulium-doped fiber 11. Specifically, the first single-frequency laser 1 includes a thulium-doped fiber 11, on which a first phase-shifted Bragg grating 12 is provided; the grating length of the first phase-shifted Bragg grating 12 is 20mm to 60mm, the phase shift value is 0 to 2π, and the phase shift position of the first phase-shifted Bragg grating 12 is located within the range of 0% to 30% of the grating length of the first phase-shifted Bragg grating 12 offset from its center to both sides.

[0062] The wavelength range of the first single-frequency laser output by the first single-frequency laser 1 configured above is 1650nm to 2150nm, the linewidth is less than 50kHz, the power is greater than 100μW, and the output laser is polarized light.

[0063] As shown in Figure 3 The thulium-doped fiber amplification module 2 includes one or more stages of thulium-doped amplifiers 21, which include a first pump light source 211 emitting first pump light, a first fiber combiner 212 for coupling the first pump light and the first single-frequency laser into a thulium-doped gain fiber 213, and a first isolator 214.

[0064] The wavelength of the first pump light is any wavelength in the range of 750nm-830nm, 1000nm-1400nm, or 1500nm-1800nm, and the core of the thulium-doped gain fiber 213 of the last-stage thulium-doped amplifier 21 is ≥10μm.

[0065] The first single-frequency laser 1 outputs a first single-frequency laser that is amplified to a maximum of 300W by the thulium-doped fiber amplification module 2.

[0066] The second single-frequency laser 3 is a single-frequency distributed feedback fiber laser with an erbium-doped gain fiber, i.e., a single-frequency distributed feedback fiber laser with an erbium-doped gain fiber. As shown in Figure 4 The second single-frequency laser 3 directly writes a second phase-shifted Bragg grating 312 on an erbium-doped fiber 311 to generate a second single-frequency laser. Specifically, the second single-frequency laser 3 includes the erbium-doped fiber 311, which is provided with the second phase-shifted Bragg grating 312; the length of the grating region of the second phase-shifted Bragg grating 312 is 25mm-60mm, the phase shift value is 0-2π, and the phase shift position of the second phase-shifted Bragg grating 312 is within the range of 0-30% of the length of the second phase-shifted Bragg grating 312 from the center of the second phase-shifted Bragg grating 312 to both sides.

[0067] The second single-frequency laser output by the second single-frequency laser 3 has a wavelength range of 1530nm-1640nm, a line width of less than 50kHz, and a power of greater than 100uW, and the output laser is polarized light.

[0068] As shown in Figure 5 The erbium-doped fiber amplification module 4 includes one or more stages of erbium-doped amplifiers 41, which include a second pump light source 411 emitting second pump light, a second fiber combiner 412 for coupling the second pump light and the second single-frequency laser into an erbium-doped gain fiber 413, and a second isolator 414.

[0069] The wavelength of the second pump light is any wavelength in the range of 900nm-1030nm or 1450nm-1530nm, and the core of the erbium-doped gain fiber 413 of the last-stage erbium-doped amplifier is greater than or equal to 10 microns.

[0070] The second single-frequency laser output by the second single-frequency laser 3 can be amplified to more than 300W by the erbium-doped fiber amplification module 4.

[0071] The first amplified laser output by the thulium-doped fiber amplification module 2 and the second amplified laser output by the erbium-doped fiber amplification module 4 enter the laser beam combination module 5, are combined into the same optical path, and form a combined laser. The laser beam combination module 5 can be composed of a fiber wavelength division multiplexer or a spatial dichroic mirror.

[0072] The combined laser output by the laser beam combination module 5 is subjected to sum-frequency conversion by the sum-frequency module 6, and forms output laser output outward. The structure of the sum-frequency module 6 is a spatial block crystal plus a temperature control module or a waveguide plus a temperature control module.

[0073] The single-frequency laser system has a wavelength range of 793.8nm-930.4nm, a maximum output power of 400W, and a laser linewidth of less than 50kHz.

[0074] The single-frequency laser system combines a single-frequency thulium-doped distributed feedback fiber laser and a single-frequency erbium-doped distributed feedback fiber laser, and further combines a thulium-doped fiber amplification module and an erbium-doped fiber amplification module, to realize single-frequency laser output in the wavelength range of 793.8nm-930.4nm through sum-frequency effect, with a maximum power of 400W. The structure is compact, is not easily affected by the environment, and does not need to be maintained, and is one of the best solutions for realizing high-performance single-frequency laser in the wavelength range of 800nm-900nm. Both the two fundamental frequency lights use single-frequency distributed feedback fiber lasers as seed sources, to realize the narrowest linewidth output after sum-frequency conversion, and have the advantages of a large wavelength tuning range and low frequency noise. In combination with a piezoelectric ceramic, wavelength rapid tuning can be realized, with a tuning bandwidth of 10kHz.

[0075] Embodiment 2

[0076] Most of the structures of Embodiment 2 are the same as those of Embodiment 1, except that the second single-frequency laser 3 is a single-frequency external cavity semiconductor laser.

[0077] The single-frequency external cavity semiconductor laser is based on a semiconductor gain chip and realizes single-frequency laser output through external feedback. The external feedback can be realized by discrete optical elements or an optical microcavity. The single-frequency external cavity semiconductor laser utilizes the short and long characteristics of the cavity length of the semiconductor laser, so that the frequency interval of adjacent longitudinal modes is large, and a filtering effect is introduced to reduce the frequency range in which laser can be generated, thereby realizing single-frequency laser output.

[0078] The structure of the single frequency external cavity semiconductor laser is shown in Figure 6 The first gain chip 321 is the gain medium, and the population inversion is realized by electric pumping. One end of the first gain chip 321 is provided with a high reflection film 322 to form a resonant cavity mirror to provide feedback. The external cavity part is composed of a filter component 323 and an output component 324. The filter component 323 is used to reduce the frequency range in which laser can be generated. The output component 324 is another mirror of the resonant cavity, which is partially transmissive and partially reflective. The transmissive part is used as the single frequency laser output, and the reflective part provides the intracavity feedback. The transmission frequency of the filter component 323 and the gain wavelength range of the first gain chip 321 determine the precise wavelength of the generated laser. The PN junction structure of the first gain chip 321, the applied current, and the resonant cavity structure determine the power of the output single frequency laser.

[0079] The second single frequency laser output by the second single frequency laser 3 has a wavelength range of 1530 nm to 1640 nm, a linewidth of less than 50 kHz, and a power of greater than 100 μW. The output laser is polarized light.

[0080] The second single frequency laser is amplified by the erbium-doped fiber amplifier module 4 to form a second amplified laser. The first amplified laser amplified by the thulium-doped fiber amplifier module 2 and the second amplified laser amplified by the erbium-doped fiber amplifier module 4 enter the laser beam combining module 5 to be combined into the same optical path to form a combined laser. The laser beam combining module 5 can be composed of a fiber wavelength division multiplexer or a spatial dichroic mirror.

[0081] The combined laser of the laser beam combining module 5 is subjected to sum frequency conversion by the sum frequency module 6 to form the output laser output outwardly. The structure of the sum frequency module 6 is a spatial block crystal plus a temperature control module or a waveguide plus a temperature control module.

[0082] The single frequency laser system described above finally outputs an output laser having a wavelength range of 793.8 nm to 930.4 nm, an output power of up to 400 W, and a laser linewidth of less than 50 kHz.

[0083] The single-frequency laser system has the advantages of narrow line width, large tuning range and high output power of the fiber amplifier, and finally obtains high-power single-frequency laser of 793.8nm-930.4nm through sum frequency effect, with the maximum power of 400W. Meanwhile, the structure is compact, not easy to be disturbed by the environment, and does not need to be maintained, which is one of the best solutions to realize high-performance single-frequency laser of 800nm-900nm at present.

[0084] Embodiment 3

[0085] Most of the structures of Embodiment 3 are the same as those of Embodiment 1, except that the second single-frequency laser 3 is a single-frequency distributed feedback semiconductor laser.

[0086] The second single-frequency laser 3 is a single-frequency distributed feedback semiconductor laser. The structure of the single-frequency distributed feedback semiconductor laser is shown in FIG. 3. Figure 7 The single-frequency distributed feedback semiconductor laser is based on a semiconductor gain distributed feedback semiconductor laser, which utilizes the characteristics of the short cavity length of the semiconductor laser, so that the frequency interval of adjacent longitudinal modes is large. The refractive index modulation is introduced in the second gain chip 331 to form a grating 332, so as to realize the integration of gain and feedback, and finally realize single-frequency laser output. The refractive index modulation period of the grating 332, the refractive index of the second gain chip 331 and the gain wavelength band determine the precise wavelength of the generated laser. The PN junction structure of the second gain chip 331 and the grating structure parameters (reflectivity, etc.) determine the power of the output single-frequency laser. The structure parameters (length) of the second gain chip 331 and the grating structure parameters (length and reflectivity, etc.) determine the line width of the single-frequency laser.

[0087] The wavelength range of the second single-frequency laser output by the second single-frequency laser 3 is 1530nm-1640nm, the line width is less than 1000kHz, and the power is greater than 100μW. The output laser is polarized light.

[0088] The single-frequency laser system is combined with a single-frequency thulium-doped distributed feedback fiber laser and a single-frequency distributed feedback semiconductor laser, and then combined with a thulium-doped fiber amplifier module and an erbium-doped fiber amplifier module, and then combined with sum frequency effect to realize single-frequency laser output of 793.8 nm-930.4 nm. The single-frequency laser system combines the advantages of narrow line width of a single-frequency fiber laser, large wavelength tuning range and large bandwidth of a single-frequency distributed feedback semiconductor laser, and fully utilizes the high output power of a fiber amplifier. Finally, high-power single-frequency laser of 793.8 nm-930.4 nm is obtained through sum frequency effect, and the maximum power can reach 400 W. The single-frequency laser system is compact in structure, is not easy to be disturbed by the environment, and does not need to be maintained. It is one of the best solutions to realize high-performance single-frequency laser of 800 nm-900 nm at present. The single-frequency laser system can combine the advantages of a single-frequency fiber laser and a single-frequency distributed feedback semiconductor laser, and realize wavelength tuning with a bandwidth of MHz level through adjusting the temperature of the two single-frequency lasers.

[0089] The single-frequency laser system can improve the frequency stability and various performance indicators of the optical clock when applied to the optical clock. The single-frequency laser can be used as lattice light in the optical clock system to cool and manipulate atoms or ions. The high-power feature can provide sufficient light field intensity to firmly constrain cold atoms or ions in the optical lattice, achieve stable and easy-to-manipulate effect, and ensure sufficient signal strength for accurate measurement. This cooling and constraint technology slows down the motion of atoms or ions to a very low temperature and energy level, thereby reducing the influence of quantum fluctuations on measurement accuracy and significantly improving the stability and accuracy of the optical clock.

[0090] The single-frequency laser system can improve the control performance of the optical tweezers on atoms when applied to the optical tweezers. Optical tweezers experiments usually involve highly precise manipulation of atoms or ions. High-power laser can provide sufficient light field intensity to achieve effective cooling process. In addition, high-power laser beams can be used to manipulate and excite atoms or ions, such as changing their motion state, energy level structure or spin state, thereby conducting quantum information processing, quantum computing and other research. The single-frequency laser system has the characteristics of low noise and narrow line width, and can also provide a stable operating environment for optical tweezers, reduce the influence of external interference on the experiment, and reduce the error caused by possible anharmonic effects, which affects the understanding of the behavior of atoms or ions. These are very important for maintaining the stability and repeatability of the experiment, especially when conducting long-time or high-precision experiments.

[0091] The present application is not limited to the above-described embodiments, and any changes in shape or structure are within the scope of the present application. The scope of the present application is defined by the appended claims, and those skilled in the art can make various changes or modifications to the embodiments without departing from the principles and the spirit of the present application, and such changes and modifications are within the scope of the present application.

Claims

1. A single-frequency laser system, characterized in that, include: The first single-frequency laser is a single-frequency thulium-doped distributed feedback fiber laser, and the first single-frequency laser is used to output the first single-frequency laser. A thulium-doped fiber amplification module, wherein the thulium-doped fiber amplification module is used to receive the first single-frequency laser and amplify the power of the first single-frequency laser to form a first amplified laser; A second single-frequency laser, which is used to output a second single-frequency laser; An erbium-doped fiber amplification module is used to receive the second single-frequency laser and amplify the power of the second single-frequency laser to form a second amplified laser. A laser beam combining module is used to combine the first amplified laser and the second amplified laser to form a combined laser beam. The sum-frequency module is used to perform sum-frequency transformation on the combined laser beam to form an output laser beam that is output outward.

2. The single-frequency laser system as described in claim 1, characterized in that: The second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser, a single-frequency external cavity semiconductor laser, or a single-frequency distributed feedback semiconductor laser.

3. The single-frequency laser system as described in claim 1, characterized in that: The first single-frequency laser includes a thulium-doped fiber, wherein the thulium-doped fiber is provided with a first phase-shifted Bragg grating; the grating region length of the first phase-shifted Bragg grating is 20mm to 60mm, the phase shift value is 0 to 2π, and the phase shift position of the first phase-shifted Bragg grating is located in the range of 0% to 30% of the grating region length of the first phase-shifted Bragg grating offset from the center of the first phase-shifted Bragg grating to both sides.

4. The single-frequency laser system as described in claim 3, characterized in that: The second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser. The second single-frequency laser includes an erbium-doped fiber, and the erbium-doped fiber is provided with a second phase-shifted Bragg grating. The grating region length of the second phase-shifted Bragg grating is 25mm to 60mm, the phase shift value is 0 to 2π, and the phase shift position of the second phase-shifted Bragg grating is located in the range of 0% to 30% of the length of the second phase-shifted Bragg grating offset from the center of the second phase-shifted Bragg grating.

5. The single-frequency laser system according to any one of claims 1 to 4, characterized in that: The first single-frequency laser has a wavelength range of 1650nm to 2150nm, a linewidth of less than 50kHz, a power greater than 100μW, and outputs polarized light. The second single-frequency laser is a single-frequency erbium-doped distributed feedback fiber laser, with a wavelength range of 1530nm to 1640nm, a linewidth of less than 50kHz, a power greater than 100μW, and outputs polarized light.

6. The single-frequency laser system as described in claim 1, characterized in that: The first single-frequency laser has a wavelength range of 1650nm to 2150nm, a linewidth of less than 50kHz, a power greater than 100μW, and outputs polarized light; the second single-frequency laser is a single-frequency external cavity semiconductor laser, with a wavelength range of 1530nm to 1640nm, a linewidth of less than 50kHz, a power greater than 100μW, and outputs polarized light.

7. The single-frequency laser system as described in claim 1, characterized in that: The first single-frequency laser has a wavelength range of 1650nm to 2150nm, a linewidth of less than 50kHz, a power greater than 100μW, and outputs polarized light. The second single-frequency laser is a single-frequency distributed feedback semiconductor laser with a wavelength range of 1530nm to 1640nm, a linewidth of less than 1000kHz, a power greater than 100μW, and outputs polarized light.

8. The single-frequency laser system as described in claim 1, characterized in that: The thulium-doped fiber amplification module includes at least one thulium-doped amplifier. The thulium-doped amplifier includes a first pump source, a first fiber combiner, a thulium-doped gain fiber, and a first isolator. The first pump source emits a first pump light. The first fiber combiner is used to couple the first pump light and a first single-frequency laser into the thulium-doped gain fiber. The first single-frequency laser is amplified in the thulium-doped gain fiber and then passes through the first isolator to form the first amplified laser.

9. The single-frequency laser system as described in claim 8, characterized in that: The wavelength of the first pump light is any wavelength among 750nm~830nm, 1000nm~1400nm or 1500nm~1800nm, and the core of the thulium-doped gain fiber of the last stage thulium-doped amplifier is ≥10μm.

10. The single-frequency laser system as described in claim 1, characterized in that: The erbium-doped fiber amplification module includes at least one erbium-doped amplifier. The erbium-doped amplifier includes a second pump source, a second fiber combiner, an erbium-doped gain fiber, and a second isolator. The second pump source emits a second pump light. The second fiber combiner is used to couple the second pump light and the second single-frequency laser into the erbium-doped gain fiber. The second single-frequency laser is amplified in the erbium-doped gain fiber and then passes through the second isolator to form the second amplified laser.

11. The single-frequency laser system as described in claim 10, characterized in that: The wavelength of the second pump light is any wavelength between 900nm and 1030nm or between 1450nm and 1530nm, and the core of the erbium-doped gain fiber of the last stage erbium-doped amplifier is ≥10μm.

12. An optical clock, characterized in that: Includes the single-frequency laser system according to any one of claims 1 to 11.

13. An optical tweezers, characterized in that: Includes the single-frequency laser system according to any one of claims 1 to 11.

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